Inching clutch with brake and acceleration controls

ABSTRACT

This invention relates to a clutch oil pressure control mechanism of the wet type. The improvements comprise means provided for automatically causing the clutch engagement on-off control to respond to movements of a conventional accelerator pedal or brake pedal so as to easily obtain no clutch or halfclutch engagement in an easier way and for substantially obviating conventional clutch-engaging shocks.

nited States Patent itano et al.

[151 3,656,600 [4 Ar. 11a, 1972 INCHING CLUTCH WITH BRAKE ANDACCELERATION CONTROLS inventors: Shin Kitano; Yutaka Momose; Kazuolshikawa; Takashi Hida, all of Kariya Japan Assignee:

Japan Filed: May 5, 1970 Appl. No.: 34,777

Foreign Application Priority Data May 7, 1969 Japan ..44/36667 June 17,1969 Japan ..44/57166 U.S. Cl ..192/.055, 137/6256, 192/.075, 192/13 R,192/109 F Int. Cl. ..B60k 21/00, B60k 29/00 Field of Search 192/109 F,.055, .094, 13 R, 192/4 A, 4 R

Aisin Seiki Kabushiki Kaisha, Kariya City,

[56] References Cited UNITED STATES PATENTS 2,695,696 11/1954 lavelli..192/109 F 2,756,851 7/1956 Collins 192/109 F 2,939,557 6/1960 Dabichet a1. 192/109 F 3,306,408 2/ 1967 Kahle 192/109 F 3,527,328 9/1970Maurice ..192/109 F Primary Examiner-Benjamin W. Wyche Attorney-Sughrue,Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT This invention relates to aclutch oil pressure control mechanism of the wet type. The improvementscomprise means provided for automatically causing the clutch engagementon-off control to respond to movements of a conventional acceleratorpedal or brake pedal so as to easily obtain no clutch or half-clutchengagement in an easier way and for substantially obviating conventionalclutch-engaging shocks.

4 Claims, 4 Drawing Figures PATENTEDAPR 18 1912 SHEET 1 BF 2 CLUTCHPRESSURE 1 i RERFECTLY CLUTCH I ENGAGING REGION 1 l I N to t. is $2CLUTCH ENGAGING HALF CLUTCHI :ENGAGING v REGION INCIIING CLUTCH WITHBRAKE AND ACCELERATION CONTROLS This invention relates generally toimprovements in and relating to automotive and the like clutchmechanisms. More specifically, it relates to an oil pressure controlmechanism adapted for automatic on-off control of clutch engagement.

It is frequently encountered with use of industrial vehicles, amongothers fork lifts, that the operator may be too tired by occupied jobswhich require repeating clutch engagement and disengagement because alarge number of shift change operations which must be carried out.

In the case of fork lifts, continued jobs must be made with the clutchkept in its semi-clutched state, resulting in a rapid wear on the clutchengaging surfaces when the clutch is of the dry type. Frequent exchangeof clutch disks is necessary to make for the safe and satisfactory forklift jobs.

It is therefore the main object of the present invention to provide asubstantially improved clutch oil pressure control mechanism adapted forobviating the aforementioned various conventional drawbacks. I

A further object is to provide a clutch oil pressure control mechanismof the above kind which utilizes the wet type clutch and the on-offcontrol of the clutch engagement is carried out automatically inresponse to the movement of the accelerator pedal or brake pedal.

It is a still further object of the invention to provide a controlmechanism of the above type wherein a no-clutch or half clutchengagement position can be more easily realized than by conventionalstructures.

A still further object is to provide a control mechanism of the abovekind wherein otherwise appearing clutch-engaging shocks may besubstantially obviated.

These and further objects, features and advantages of the invention willbecome more apparent when reading the following detailed description ofthe invention by reference to the accompanying drawings illustrative ofseveral preferred embodiments of the invention.

In the drawings:

FIG. 1 is a schematic and substantially sectional view of thearrangement for the oil pressure control of an automotive clutch unitaccording to the first embodiment of the invention.

FIG. 2 is an enlarged substantially sectional view of the clutch unitshown in FIG. 1.

FIG. 3 is an explanatory chart of the clutch pressure plotted againstthe clutch engagement period realizable, by way of example, with use ofthe clutch pressure control arrangement substantially shown in FIG. 1.

FIG. 4 is a schematic explanatory view of the second embodiment of thepresent invention.

Referring now to the accompanying drawings, especially FIG. 1 thereof,the numeral represents a pump only schematically shown, having a suctioninlet 100 which is connected through a suction piping 100 to an oilreservoir 11 and a delivery output 10b which is kept in fluidcommunication with a delivery duct 12 which connected fluidically to aregulator valve assembly generally shown at 13, or more specifically anoil reception chamber 25 thereof. Thus, it will be seen that when theoil pump 10 is operated, oil is sucked by the latter from the reservoir11 to the reception chamber 25 of the regulator valve assembly 13.

From the delivery duct 12, a duct 14 is branched off and leads through aflow-reducing orifice 15 formed therein to a clutch assembly tolubricate and cool its clutch plates, as will be more fully describedhereinafter in connection with FIG. 2.

Regulator valve assembly 13 comprises a small diameter bore 17 and alarge diameter bore 18 arranged coaxially with each other and thusforming in combination a stepped common valve bore, the former bore 17being formed with drain chambers 19, 20, and 21 which are formed in turnwith drain ports 22, 23, and 24, respectively. The aforementionedchamber 25 is positioned at an intermediate point between the chambers19 and 20, as shown, and kept in fluid communica tion with acommunication duct 26.

A spool valve member 36 is slidably mounted within the bore 17, thelatter being formed with a first concentric land 27 which has a smallerinside diameter than that of corresponding bore 17 and land 28 andsubstantially equal to the outside diameter of valve land 36a andextends between the chambers 19 and 25. The valve bore is further fonnedwith a second concentric land 28 which has a substantially equal insidediameter as the outside diameter of a valve land 36b and bore 17 andextends between the chambers 20 and 25.

A snap ring 29 is firmly held in the wall of the large diameter boreelement 18 at an intermediate point between both extremities thereof,said bore element 18 being kept at its inner end 18a in fluidcommunication with the small diameter bore element 17, while theopposite or outer end 18b is closed by a plug 30 which is held firmly inposition by means of a snap ring 31. The plug is provided with a sealingring 32 for the prevention of oil leakage through unavoidable small gapsformed between the plug and the related wall part of the bore element.

A chamber 34 is formed at an intermediate point between snap ring 29 andplug 30 for establishing fluid communication with a connection duct 33.Between the inner end 36d, having a reduced cross-section as shown, ofthe spool member 36, and the inner end of slidable piston 37, there 18provided under compression a compression coil spring 35, being calledthe regulator valve spring, which urges with its inner end 350resiliently the spool 36 in the left-hand direction in FIG. I and thusthe outer end of land 36a thereof abutting against the outer end wall17a of the elongated valve bore 17-18. The opposite or outer end of thespring, abutting upon the piston 37 is shown at 35b. Normally, thispiston 37 abuts against snap spring 29.

Spool valve member 36 comprises first spool land 36a adapted for slidingmovement within the bore part defined by the first bore land 27; secondspool land 36b mounted slidably within the bore part defined by thesecond bore land 28; and third land 36c adapted for sliding within thebore element 17.

When pressure oil is conveyed from the pump 10 through duct 12 toreception chamber 25 of the regulator valve 13, the oil pressure actsupon the spool valve 36, and the latter is hydraulically urged to slidein the right-hand direction in FIG. 1 because the diametral differencebetween lands 36b and 36a and against the spring force at 35, therebythe chamber 25 being brought into fluid communication with the drainchamber 20 and excess oil being discharged through the related drainopening 23. In this way, the oil pressure prevailing in the chamber 25is regulated to a certain value in response to the now established loadon the spring 35. This spring load is determined by the displacement ofpiston 37 which is urged hydraulically by being subjected to oilpressure supplied from a hydraulic circuit to be described and throughsaid duct 33 to the related chamber 34. The oil pressure supplied to thereception chamber 25 is conveyed through connection duct 26 kept incommunication therewith to reception chamber 43a of an inching valveunit generally shown at 38.

The inching valve unit 38 is provided with an elongated bore 39 open atone end 39a thereof. Within this bore 39, a spool valve generally shownat 40 is slidably mounted and one end 40a is kept in contact with a cam41 which is mounted rotatably and connected with a conventionalfoot-operated brake pedal 99 for rotation with movement thereof,although not specifically shown for simplicity. Outer end 40a of thevalve spool 40 is kept in sliding contact with the rotatable cam, whilethe opposite or inner end 40b of the spool is kept in pressure contactwith the inner end 420 of an inching valve spring 42, the outer end 42bof the latter abutting against the closed end wall 39b of said bore 39.The spool valve 40 comprises somewhat elongated land 400 which isslidable at the bore end 39a; a reduced step part 40d; a truncated conepart 40e; and an end cylindrical part 40f forming a land which isslidable in the bore 39. There is a liquid chamber 43 which is formedbetween the spool 40 and the wall of bore 39 and provided in turn withan oil inlet 43a and an outlet 43b. The inlet 43a is kept in fluidcommunication with said duct 26 and the outlet 43b communicates with aconnection duct 44. The bore 39 is formed with drain chambers 45 and 46which are provided in turn with drain ports 47 and 48, respectively.

With the brake, not shown, kept in its non-operating conditions,pressure oil supplied to said chamber 43 will be conveyed through saidoutlet 43b to duct 44.

When the brake pedal 99 is depressed on the other hand, motion istransmitted therefrom to the cam 41 which is thus rotated and the valvespool 40 is moved in the right-hand direction in FIG. 1 against theaction of spring 42 until the reduced and stepped cylindrical portion40d covers gradually the supply opening 43a which is thus substantiallyclosed to provide a throttling means. At the same time, the taper part40s is brought to such a position that a fluid communication between thechamber 43 and the drain port 47 of chamber 45, thus the oil pressureprevailing in the chamber 43 being dropped. In this way, asemi-clutching condition is realized during the idle stroke of the brakepedal.

Pressure oil is conveyed from inching valve 38 through said duct 44 to acut-off valve unit 49. This unit 49 is formed with a bore 50 open at itsone end 50a. There is provided a solenoid 51 adjacent to andconcentrically with said opened bore end 50a an electromagnetic solenoid51 which is provided coaxially and slidably with an armature in the formof a push rod 52. The numeral 53 represents a cut-off valve spring whichis mounted within the bore 50. The outer end 53a of said spring 53 abutsagainst the bore end wall 50b, while the opposite or inner end 5312 iskept in pressure engagement with the outer end 54a of valve spool 54which is slidably mounted in the bore 50. Under the influence of cut-offvalve spring 53, the inner end 54b of valve spool 54 is kept in pressureengagement with the solenoid armature 52. Valve spool 54 is formed withtwo lands 54c and 54d which have proper dimension so as to be slidablewithin the bore 50. A liquid chamber 55 is formed between valve spool54, and base 50, said chamber being provided with supply port 55a keptin fluid communication with 44; and further with an outlet port 55bcommunicating with duct 56. Drain chambers 57 and 89 are provided in thebore and formed with drain ports 57a and 89a, respectively. Solenoidcoil 51 is arranged to be energized by supply of current from anelectric circuit 59 which is provided with a current source, preferablya vehicle battery, not shown, and arranged operable by closure ofattached switch 58a when a conventional accelerator pedal 58 is kept inits idle position; this pedal may be replaced with equal results by aconventional shift bar, not shown, when necessary. In other words,solenoid 51 is kept energized with the accelerator pedal 58 positionedin its released state. With energization of solenoid 51, the armature 52is brought into actuation to advance, thereby valve spool 54 beingdisplaced against the spring action at 53. In this way, valve land 54dis brought into such position that the hitherto established fluidcommunication between ducts 44 and 46 is positively interrupted, whileduct 56 is brought into communication with the drain port 57a of drainchamber 57, resulting in the oil pressure in clutch chamber 60 reducedto nil and the clutch being brought into disengagement.

When the accelerator pedal 58 is depressed, the solenoid 51 isde-energized and the armature or solenoid push rod 52 will return to itsoriginal position by the urging action exerted thereupon through theintermediary of valve spool 54 by cutoff valve spring 53. Thus, thefluid communication between ducts 44 and 56 is recovered.

In this way, oil pressure prevailing within clutch chamber 60 iselevated and the clutch is brought into re-engagement.

Oil pressure supplied from cut-off valve 49 is conveyed through ducts 56and 61 to orifice valve 62. On the other hand, oil pressure is conveyedfrom said duct 56 through duct 63 to a quick supply valve 64.

Orifice valve 62 is provided with a bore 65 which is kept in fluidcommunication at its both ends with ducts 61 and 33, respectively.

The numeral 66 represents an orifice valve spring mounted in the bore65; the upper end 66a abuts through a seat ring 67 against theshouldered upper end 650 of said bore, while the lower end 66b abutsthrough a piston 68 against a snap spring 67a held firmly in position inthe wall defining said bore 65. The piston 68 is formed with aconcentric orifice opening 680.

A liquid chamber 69 is defined by the bore wall 65 and said piston 68and communicates fluidically with duct 61, on the one hand, and throughthe orifice 68a with said duct 33. A drain chamber 70 is formed withinsaid bore 61 and provided in turn with a drain port 700. Pressure oilsupplied from duct 61 to said chamber 69 is conveyed through the orifice68a to said duct 33.

When the brake pedal 99 is depressed or the accelerator pedal 58 isreleased from foot pressure for disengaging the clutch, theaforementioned hydraulic circuit is interrupted by the valve spool 54and then brought into fluid communication with said drain port, thus theoil pressure being caused to drop.

When the pressure oil in the chamber 69 is drained in this way, piston68 will be moved against the action of orifice valve spring 66, thus thedrain port 70a of drain chamber 70 is communicated with duct 33. Oilpressure in the chamber 60 is thus rapidly released and the clutch isbrought into its positively released state.

Quick supply valve 64 is provided with an elongated and stepped borecomprising a small diameter bore 71 and a large diameter bore 72. Avalve spool 73 is slidably mounted in the large diameter bore 72, acompression coil spring 74 being inserted between one end 73a of saidvalve spool and an end wall 71a of said small diameter bore 71. Underthe action of quick supply valve spring 74, the valve spool 73 is keptin abutment with the opposite end wall at 72a of said bore 72, the spool73 being formed with two lands 73b and 730 for making the spool slidablealong the bore 72. The land 730 is positioned axially at a certainpredetermined distance from one end 73d of the spool 73. A chamber 75 isdefined by the bore wall 72 and said spool lands 73b and 73c, and formedin turn with a supply port 750 kept in fluid communication with duct 63and with an outlet port 75b communicating with duct 76. A liquid chamber77 is defined at one end 72a of large diameter bore 72 by the end 73d ofvalve spool 73 and said land 73c. A communication duct 73e is boredthrough the land 73c in the axial direction thereof for establishingfluid communication between chambers 75 and 77.

A drain chamber 78 is formed in the small diameter bore 71 and formedwith a drain port 78a. Oil pressure is conveyed from duct 63 to chamber75, and thence through communication duct 73e to chamber 77. When oilpressure in the chamber 75 exceeds a certain predetennined value, thehydraulically urged valve spool 73 moves against the action of quicksupply valve spring 74 until it will be brought into abutment with ashoulder 79 which defines the critical plane between the bore elements71 and 72. At this stage, the land 730 of valve spool 73 is kept in sucha position that it interrupts the hitherto established fluidcommunication between the ducts 63 and 76.

As seen from FIGS. 1 and 2 in combination, the hydraulic pressureconveyed through the duct 81 is conveyed to the clutch chamber 60 andurges the piston 80 to move towards clutch plates package 16. It shouldbe noted that the dimension and arrangement of the related parts are soselected that the fluid connection between the ducts 63 and 76 ismaintained and thus a larger quantity of pressure oil is supplied to theclutch chamber 60, until directly before the engagement of clutch piston80 with plates package 16. Upon said communication, hydraulic engagementbetween 63 and 76 is interrupted by valve sleeve 73 of the quick supplyvalve unit 64 and the supply of pressure oil to duct 81 is carried outonly through orifice valve 62, thereby otherwise possible shock at theengagement of the clutch can be substantially obviated.

The pressure oil supplied through orifice valve 62 and quick supplyvalve 64, when the latter is in its operating condition, is

conveyed from duct 76 through duct 33 to chamber 34 so that the piston37 is displaced against the action of regulator valve spring 35. In thisway, the load or. the spring 35 is gradually varied so as to adjust theline pressure gradually to a higher value.

The supply pressure is conveyed through duct 81 and acts uponaccumulator piston 87 which is slidably mounted in one end of a bore 83,while in the opposite end of the latter, a plug 84 is sealingly receivedand abuts against a snap ring 85 held firmly in position at the bore end83a. An elongated compression spring 86 is inserted in the bore, one end86a of said spring abutting against said plug 84 and the opposite end86b being kept in pressure engagement with accumulator piston 07 whichabuts thus under pressure against the wall defining the duct 81. Thebore 83 is formed with a drain chamber 88 which is formed with a drainport 88a.

The accumulator piston 87 is designed and arranged so that uponactuation of the quick supply valve 64 hydraulically by the supply oilpressure, it moves towards the right against the action of spring 86.Therefore, the pressure oil supplied from the accumulator 02 is conveyedthrough duct 81 to clutch chamber 60, as was referred to hereinabove, soas to actuate the clutch piston 80 for bringing the clutch into itscoupled condition.

In the following, a general description of the operation of the clutchoil pressure control arrangement will be given.

When the drive engine, not shown, of the vehicle is started, the oilpump mechnically coupled with the drive engine as done conventionally,although not shown, delivers pressure oil which is utilized forlubricating and cooling the clutch as con ventionally done, said oilbeing conveyed to the control oil circuit and subjected at first topressure adjustment in the regulator valve 13, thence to the inchingvalve 38. When the brake pedal 99 is depressed to a full degree underthese operating conditions, valve spool 40 is displaced against theaction of inching valve spring 42, resulting in the supply pressure oilbeing drained off at 47. Therefore, no oil pressure is accumulated inthe clutch chamber 60 and the clutch is brought into its completedisengagement.

With the brake pedal 99 in its released condition and simultaneously,the accelerator 50 is also in its released condition, the thus energizedsolenoid 51 of cut-off valve 49 will actuate its push-rod type armature52 so as to move the valve spool 54 against the action of cut-off valvespring 53 and the supply oil pressure is drained off at 57a. Thus, theclutch is again brought into its uncoupled condition.

In the case of a starting period, when the starting is requiredgradually to perform or a half-clutch operation to be brought about, thebrake pedal is gradually released and the accelerator pedal 58 isdepressed gradually. In this case, the supply pressure oil is throttledto a substantial degree by the reduced diameter land 40d of valve spool40 of inching valve 38 and then subjected to a pressure reduction in theaccumulator 82; Therefore, oil pressure in the circuit 33 is reduced andthe oil pressure rise in the valve 13 is retarded. Thus, oil pressure inthe clutch chamber 60 will rise gradually and the vehicle starts againgradually.

When it is desired to make a rapid start of the vehicle, the brake pedal99 is quickly released and the accelerator pedal is depressed suddenly.The supply pressure is supplied through said quick supply valve 64 tothe clutch chamber 60 until directly before the engagement of the clutchplates 60. Then, the valve spool 73 of quick supply valve 64 ishydraulically displaced to such a position that the hitherto establishedfluid communication is thereby interrupted, resulting in the throttlingeffect to the pressure oil at the orifice valve 62 and the oil pressurein accumulator 81. In this way, oil pressure in the circuit 33 isreduced and the rise of oil pressure at regulator 13 is retarded. Riseof pressure in clutch chamber 60 is retarded and the relation betweenthe oil pressure in clutch chamber 60 and the clutch-engaging time willbecome as shown in FIG. 3 by way of example. As seen from this chart,the normally appearing shock occurs at the clutch-engaging instance.Also in the case of shift change operation, it is only necessary thatthe accelerator pedal 58 be once released and upon bringing about ashift, the accelerator pedal 58 is depressed.

As will be seen from the foregoing, the clutch oil pressure controlarrangement according to this invention utilizes a wet type clutch andin the case of the on-off control operation thereof, the clutch isautomatically brought into engagement in response to the movement ofaccelerator pedal or brake pedal for the purpose of reducing thenecessary time period from the initial indication point of aclutch-engaging operation to the comencement of the clutch engagement,as short as possible. In addition thereto, the necessary time periodfrom initial clutch engagement to full clutch engagement can be,according to our experiment, set to an ideal short length such as,preferably, 1.0-1.5 seconds for industrial and personel vehicles.

It was further found that clutch engagement shocks conventionallyappearing at the start of the vehicle or in a shift change operation canbe substantially obviated.

Next, referring to FIG. 4, a second embodiment will be described indetail.

The numeral 101 denotes an oil reservoir and 102 a pump which ismechanically connected with a drive engine of an automotive vehicle,although not specifically shown in the drawing for simplicity.

The pump 102, shown only in a highly simplified schematic way, isinserted in a piping 104 and arranged to suck oil therethrough from saidreservoir 101 through a suction strainer 103 which is attached to thelower end of said piping and immersed in a pool of oil contained in thereservoir.

A regulator valve unit 105 is formed with an elongated bore 106 in whicha regulator valve member 107 is slidably mounted and urged by a returnspring 100 inserted in said bore. Regulator valve member 107 is formedwith three lands 107a, 107b, and 1070, said return spring abuttingagainst the last land 1070 with its inner end and kept in pressureengagement with the right-hand end wall of said bore 106 with itsopposite or outer end. A first liquid chamber 109 is formed between thelands 107a and 107b and within said bore 106, and a second chamber 110is formed at the left-hand end of said bore 106 and defined by thecorresponding bore end wall and the first valve land 107a. Chamber 109is formed with an inlet port 111 which is kept in fluid communicationwith pip ing 104 for receiving pressure oil delivered from pump 102, andwith an outlet port 113 kept in fluid communication with a piping 112which leads to a chamber formed in a clutch operator generally shown at119. The chamber 110 is formed further with a port 115 which isconnected with said piping 112 through a short connection pipe 114formed therein with an orifice 113.

The bore 106 is formed further with a drain port 116 which is connectedwith a drain piping 117 leading to oil reservoir 101. The piping 112 hasformed therein an orifice 118 at an intermediate point between theconnection pipe 114 and the unit 119 which is fitted therein with clutchplates package 121, thereby the clutch plates consisting the package 121being always kept in optimally lubricated condition.

From oil feed piping 104, a branch pipe 123 is connected to an inchingvalve unit generally shown at 122 which comprises a valve body 124fixedly attached to a valve casing 125.

On the upper surface of the body 124, an inching valve member 129- ispositioned under pressure and sealingly therewith with its bottom flange129a by means of a sealing ring 126 made of rubber or the like materialand serving as a valve seat, the main body of said valve 129 beingslidably positioned on the outer peripheral surface of a tube-likeprojec' tion 1240 made integral with the valve body 124.

A cone seat a is formed in the valve case 125, said seat being formedwith an opening 128 which is kept in fluid communication with thecommunication pipe 123. A cone-shaped valve land 12% is formed on theend of valve 129 and engages with cone seat 125a. The main body of theinching valve 129 is made into substantially a cylindrical cup aroundwhich there is provided a coil spring 130 tensioned between the valvecasing 125 and the valve flange 129a.

With the brake pedal 131 kept in its released condition, the inchingvalve 129 is kept in the position shown, thus a liquid chamber 132formed within the valve is interrupted from fluid communication with aduct 127 formed through the valve body 124. Under these conditions,however, the valve proper at 12% formed on top end of the member 129defines a valve gap between the inching valve and its seat, thus saidchamber 132 being is in fluid communication with the pipe 123 throughvalve opening 128.

The interior space of inching valve element 12% is kept in fluidcommunication through a duct 134 and with a hydraulic brake pressurepiping 135, the latter being fluidically connected with a piping 137which extends from the outlet of a conventional master cylinder 136 to awheel cylinder 138a adapted for performing a wheel braking at 138 asconventionally.

Numeral 140 represents a piping which extends from a port 141 formedthrough the wall of valve housing 125 and kept in fluid communicationwith the interior chamber 132, to a port 150 formed through the housing142a of a cut-off valve unit 142.

A pipe 143 connects the duct 127 with oil reservoir 101. The cut-offvalve unit 142 is formed with a bore 144 having an open end as shown at144a. This open bore end 144a is, however, sealedly closed by anelectromagnetic solenoid 145 which is provided with a centrally andaxially arranged armature in the form of push rod 146.

A cut-oi? valve proper 147 is slidably mounted in the bore 144, saidvalve proper having two lands 147a and 147b. A return coil spring 148 isinserted in the right-hand bore end for urging the valve proper 147against the push rod 146.

A liquid chamber 149 is formed between the lands 147a and l47b andwithin the bore 144 and kept in communication through a port 150 withsaid piping 140, on the one hand; and through an outlet port 151 with apiping 152 leading to the clutch chamber 120. An orifice 153 is providedin the piping 152 for the adjustment of oil flow therethrough.

Solenoid 145 is connected to leads 156 fitted with battery 200 and anon-off control switch 155, the latter being arranged to be actuated uponby a conventional automotive throttle pedal 154. This electric circuit156 is so arranged that when the pedal 154 is kept in its releasedposition, switch 155 is brought into its operating position so as toenergize the solenoid.

With the solenoid 145 thus energized, the push-rod 146 is moved inwardsfor urging the cut-off valve proper 147 to move to the right against theaction of return spring 148. By this operation, the land 147a of thevalve proper 147 is brought to a position wherein the discharge port 150is closed. On the other hand, valve end 147b recedes from the shownposition covering the drain port 157, thereby the chamber 149 beingbrought into fluid communication with drain piping 158 which isfluidically connected with said drain piping 143 coming from the inchingvalve.

The operation of the above clutch oil pressure control arrangement is asfollows.

When the automotive drive engine is brought into starting and the pump102 is operated, oil is sucked from oil reservoir 101 through strainer103 and delivered to a piping 104, thence to chamber 109 of regulatorvalve 105. The thus supplied pressure oil is conveyed from chamber 109to piping 112. Part of this pressure oil is then subjected to a flowcontrol action at the orifice 118, and then conveyed to chamber 120 ofclutch actuating device 119 for lubricating and cooling clutch plates121 in the clutch chamber 120. Another part of the pressure oil passesorifice 113 in connection pipe 114 to chamber 110 so as to displace theregulator valve proper 107 against the action of spring 108.

With the displacement of regulator valve 107, a part of pressure oil isdischarged from drain port 116 for attaining a predetermined pressurelevel.

The drain oil discharged from port 116 is conveyed through piping 117 tooil reservoir 101. On the other hand, the pressure-regulated oil at theregulator valve unit is conveyed through a branch pipe 123 to chamber132 of inching valve 122 which is adapted for actuation in response tothe brake oil pressure; thence through piping 140 to cut-off unit 142.

The supply pressure oil passed through the inching valve 122 is conveyedthrough piping 140 to the chamber 149 of oil pressure cut-off valve 142.

When, under these conditions, the throttle pedal 154 is depressed, theswitch 155 is broken and the supply pressure oil in chamber 149 ofcut-off valve unit 142 is conveyed into piping 152 and flows throughorifice 153 to the chamber of clutch actuator 119, thereby bringing theclutch into it actuating state.

When brake pedal 131 is depressed at this stage, brake pressure oil isdelivered, as conventionally, from master cylinder 136 through piping137 to wheel cylinder 138a of the wheel brake 138, on the one hand, andthrough brake pressure oil supply piping and duct 134 to the interiorspace of inching valve proper 124. On account of the presence of apressure difference between the spring pressure at 130 added with theregulated oil pressure at regulator 105 acting upon the top workingsurface of the inching valve 129, on the one hand, and the hydraulicbrake pressure supplied to the interior space of the inching valveproper, on the other hand, and when the latter or brake pressure ishigher, the inching valve 129 is moved upwards from contacting positionwith the valve seat 126, thereby said chamber 132 is brought intocommunication with duct 127.

The pressure-adjusted oil pressure to a certain constant value andprevailing in chamber 132 is conveyed through drain pipe 143 back to oilreservoir 101, and at the same time, the valve head 12% of inching valve129 will occupy a nearer position to its valve seat 125a so as toprovide a kind of orifice in effect. In this way, the pressure oilsupplied to clutch chamber 120 of clutch actuator 119 will be throttled.With this intermediate position of the inching valve proper in advanceof engagement thereof with the valve seat and with the throttle pedal154 kept in its depressed position, a semiclutched position is realizedand thus the vehicle can be inchingly driven, regardless of the enginerevolutional speed.

With the brake pedal 131 positioned at its fully depressed position, theinching valve head 12% is brought into full contact with the valve seat12511. In this way, the fluid comm unication between the pipe 123 andthe chamber 132 is interrupted, while the piping 140 and the drain pipe143 are brought into fluid communication with each other. Therefore, theclutch plates package 121 in the clutch actuator 119 is brought into itsuncoupled position.

On the contrary, when the throttle pedal 154 is released, the switch 155is actuated to energize the solenoid 145 for advancing the push rod 146.In this way, cut-off valve proper 147 is displaced against the action ofsnap ring. Then, the hitherto established interruption of fluidcommunication between chamber 149 and piping 158 is broken. Fluidcommunication between piping 152 and drain piping 158 is alsoestablished. Clutch plates 121 are brought into its non-engaging state.

In the second embodiment so far shown and described, the inching valveunit is provided with a valve member having valving means at its bothends so that no appreciable difference in sliding resistance can beencountered by application of lateral forces. The clutch actuator can bepositively fed with an oil pressure in response to the stroke of thebrake pedal; thus the driver can feel favorable and pleasant brakingfoot touch.

The embodiments of the invention in which an exclusive property orprivilege is claimed are as follows:

1. A clutch oil pressure control arrangement, comprising in combination:

a. an oil pressure supply source;

b. a clutch actuating means adapted for receiving oil pressure from saidsource and being actuated thereby;

c. oil passage means adapted for establishing fluid communicationbetween said source and said clutch actuating means;

d. an oil pressure regulator valve means provided in said passage meansfor adjustment of oil pressure being conveyed to said clutch actuator;an inching valve means provided in said passage means between saidregulator valve means and said clutch actuating means for throttling theoil pressure regulated by said regulator valve means, said inching valvemeans operatively connected to a brake pedal and responsive to thedegree of actuation of said brake pedal; and

. a cut-off valve means provided in said passage means between said oilpressure regulator valve means and said clutch actuating means, saidcut-off valve means being operatively connected to an engine acceleratorpedal for on-off control of the oil pressure in said passage means andin response to the degree of actuation of said accelerator pedal.

2. A clutch oil pressure control arrangement as claimed in claim 1further comprising:

a. an orifice valve means provided in said passage means between saidcut-off valve means and said clutch actuating means, said orifice valvemeans having an orifice therethrough for conveying oil pressure throughsaid orifice valve means to said clutch actuating means when oilpressure at the side of said cut-off valve means is higher than oilpressure at the side of said clutch actuating means and adapted fordraining the oil pressure at the side of said clutch actuating meanswhen the oil pressure prevailing at the side of said clutch actuatingmeans is higher than the oil pressure at the side of said cut-off 10valve means; and

b. a quick supply valve means provided in said passage means betweensaid cut-ofi' valve means and said clutch actuating means forinterrupting oil pressure being conveyed to said clutch actuating meanswhen the oil pressure exceeds a predetermined value, said quick supplyvalve means being connected in parallel with said orifice valve means toallow oil pressure to be supplied to said clutch actuating means throughsaid orifice upon establishment of said interruption; and branch oilpassage means communicating said regulator valve means with said passagemeans at a point between said quick supply valve means and said clutchactuating means for bringing said passage means and said regulator valvemeans into fluid communication for controlling said regulator valvemeans in response to the oil pressure prevailing in said clutch actuatormeans.

3. A clutch oil pressure control arrangement as claimed in claim 2,further comprising an accumulator means provided in said passage meansbetween the combination of said orifice valve means and said quicksupply valve means and said clutch actuating means, for bringing clutchplates of the latter into their engaged position upon actuation of saidquick supply valve means.

4. A clutch oil pressure control arrangement as claimed in claim 1,wherein said cut-off valve means comprises a solenoid adapted for beingenergized upon release of said accelerator pedal, and a valve forinterrupting oil pressure supply to said clutch actuating means uponenergization of said solenoid and for draining the oil pressureprevailing in said clutch-actuating means.

1. A clutch oil pressure control arrangement, comprising in combination:a. an oil pressure supply source; b. a clutch actuating means adaptedfor receiving oil pressure from said source and being actuated thereby;c. oil passage means adapted for establishing fluid communicationbetween said source and said clutch actuating means; d. an oil pressureregulator valve means provided in said passage means for adjustment ofoil pressure being conveyed to said clutch actuator; e. an inching valvemeans provided in said passage means between said regulator valve meansand said clutch actuating means for throttling the oil pressureregulated by said regulator valve means, said inching valve meansoperatively connected to a brake pedal and responsive to the degree ofactuation of said brake pedal; and f. a cut-off valve means provided insaid passage means between said oil pressure regulator valve means andsaid clutch actuating means, said cut-off valve mEans being operativelyconnected to an engine accelerator pedal for on-off control of the oilpressure in said passage means and in response to the degree ofactuation of said accelerator pedal.
 2. A clutch oil pressure controlarrangement as claimed in claim 1 further comprising: a. an orificevalve means provided in said passage means between said cut-off valvemeans and said clutch actuating means, said orifice valve means havingan orifice therethrough for conveying oil pressure through said orificevalve means to said clutch actuating means when oil pressure at the sideof said cut-off valve means is higher than oil pressure at the side ofsaid clutch actuating means and adapted for draining the oil pressure atthe side of said clutch actuating means when the oil pressure prevailingat the side of said clutch actuating means is higher than the oilpressure at the side of said cut-off valve means; and b. a quick supplyvalve means provided in said passage means between said cut-off valvemeans and said clutch actuating means for interrupting oil pressurebeing conveyed to said clutch actuating means when the oil pressureexceeds a predetermined value, said quick supply valve means beingconnected in parallel with said orifice valve means to allow oilpressure to be supplied to said clutch actuating means through saidorifice upon establishment of said interruption; and branch oil passagemeans communicating said regulator valve means with said passage meansat a point between said quick supply valve means and said clutchactuating means for bringing said passage means and said regulator valvemeans into fluid communication for controlling said regulator valvemeans in response to the oil pressure prevailing in said clutch actuatormeans.
 3. A clutch oil pressure control arrangement as claimed in claim2, further comprising an accumulator means provided in said passagemeans between the combination of said orifice valve means and said quicksupply valve means and said clutch actuating means, for bringing clutchplates of the latter into their engaged position upon actuation of saidquick supply valve means.
 4. A clutch oil pressure control arrangementas claimed in claim 1, wherein said cut-off valve means comprises asolenoid adapted for being energized upon release of said acceleratorpedal, and a valve for interrupting oil pressure supply to said clutchactuating means upon energization of said solenoid and for draining theoil pressure prevailing in said clutch-actuating means.